Heavy Snow Warning 9, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
1220 PM ADT TUE APR 15 2008

.DISCUSSION...

UPPER AIR...
SHORT WAVE TROUGH WILL MOVE EASTWARD ACROSS THE FORECAST AREA
THROUGH 00Z THU. RIDGING OVER THE BERING SEA WILL MOVE
EAST...BUILDING OVER THE ALASKA MAINLAND OVER THE WEEKEND.
HIGH CONFIDENCE IN THE WEEKEND FORECAST WITH GOOD AGREEMENT
BETWEEN ECMWF/GFS...ALL GFS ENSEMBLE MEMBERS SHOWING RIDGE
FORECAST AND ENSEMBLE SPREAD IS LOW THROUGH THE WEEKEND.

AFTER THE WEEKEND...OPERATIONAL GFS AND GFS ENSEMBLES SUGGESTING
EASTWARD MOVEMENT OF THE RIDGE INTO CANADA...ECMWF MAINTAINING
A STRONG UPPER HIGH FROM NORTHEAST ALASKA EASTWARD. CONFIDENCE
IN THE UPPER AIR FORECAST BEYOND THE WEEKEND DIMINISHES
RAPIDLY AS OPERATIONAL GFS/ECMWF BECOME QUITE DIVERGENT...AS
DOES THE GFS ENSEMBLE SUITE. EVEN IF THE UPPER RIDGE DOES
SHIFT EASTWARD...SOUTHERLY FLOW OVER THE ALASKA INTERIOR WOULD
MAINTAIN MILD TEMPERATURES...AT LEAST EARLY IN THE WEEK.
850 MB TEMPERATURES IN THE INTERIOR WILL RISE TO NEAR 0C BY THE
WEEKEND AS THE RIDGE BUILDS.

SURFACE...
996 MB LOW 250 MILES NORTH OF DEMARCATION POINT WILL WEAKEN TO
996 MB OVER SOUTHERN BANKS ISLAND BY 00Z THU. WESTERLY GALES
OVER PKZ245-AKZ204 SHORELINE WILL DIMINISH TO BELOW GALE BY
MIDNIGHT TONIGHT...CONTINUING TO DIMINISH THROUGH 00Z THU.

NORTHWESTERLY UPSLOPE FLOW WILL DEVELOP TONIGHT OVER ZONES
224-226 AS THE NORTHERN GULF LOW MOVES EAST...ASSISTED BY
SOME SHARPENING AND DEEPENING OF THE SOUTHERN PART OF THE
SHORT WAVE AS IT MOVES EASTWARD. SIGNIFICANT SNOW EXPECTED
IN THE SOUTHEAST PART OF ZONE 224 AND MUCH OF ZONE 226...
SNOW ADVISORIES GOING UP ON THE AFTERNOON FORECAST TRANSMISSION.

1004 MB LOW ABOUT 600 MILES WEST OF WRANGEL ISLAND PROGGED
TO REACH THE NORTHWEST CAPES BY 00Z THU...FILLING TO A VERY
WEAK 1016 MB CENTER. THIS WEAKENING SYSTEM MAY BRING SOME
SNOW TO THE WEST COAST AREAS LATE TUE NIGHT AND WED.

DEVELOPING 1000 MB LOW ABOUT 400 MILES SOUTH OF THE KAMCHATKA
TIP EXPECTED TO MOVE NORTHWARD OFF THE EASTERN KAMCHATKA
COAST THROUGH 12Z THU...WITH A NEW CENTER DEVELOPING AND
MOVING TO THE WRANGEL ISLAND AREA BY 12Z SAT. ASSOCIATED FRONT
MAY BRING PRECIPITATION TO THE WEST COAST LATE IN THE WEEK.
AT THIS TIME...ASSOCIATED WINDS OVER THE NORTHERN BERING ARE
EXPECTED TO REMAIN BELOW GALE FORCE.

GFS/ECMWF IN GENERALLY GOOD AGREEMENT ON THE HANDLING
OF THESE LOW CENTERS THROUGH 12Z SAT.

&&

.FIRE WEATHER...NONE.

&&

.HYDROLOGY...
SIGNIFICANTLY WARMER TEMPERATURES IN THE INTERIOR FROM SATURDAY
AT LEAST INTO THE MIDDLE OF NEXT WEEK...INDICATED BY CURRENT
ECMWF AND GFS AS STRONG UPPER RIDGE BUILDS. 850 MB TEMPERATURES
LIKELY REACHING 0C...WHICH WOULD SUPPORT DAYTIME HIGH TEMPERATURES
WELL INTO THE 50S...MARKING THE START OF RAPID MELTING OF THE
SNOWPACK...WHICH HAS CHANGED LITTLE DURING THE FIRST HALF OF APRIL
DUE TO MAINLY BELOW NORMAL TEMPERATURES WITH ADDITIONAL SNOWFALL
OCCURRING. THE MOST RECENT SNOWFALL EVENT IN THE FAIRBANKS AREA WAS
A VERY SLUSHY ONE...WITH 0.5 INCH OF WATER EQUIVALENT REPORTED AT
THE FAIRBANKS AIRPORT. CURRENT SNOW DEPTH OF 13 INCHES AT FAIRBANKS
IS ABOUT 25% ABOVE AVERAGE FOR THE DATE.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SNOW ADVISORY AKZ224-AKZ226.

GALE WARNING PKZ245.

&&

RF APR 08